1. Field
Example embodiments relate to a semiconductor memory device that includes an address coding method for a multi-word line test, for example, an address coding method to test a semiconductor memory device having a cell block row selection circuit.
2. Description of the Related Art
Conventionally, a data storage space of semiconductor memory devices may be a memory cell array such as a Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), and Parameter Random Access Memory (PRAM), for example. The memory cell array may include a plurality of memory cells coupled to intersections of word lines and bit lines.
An access operation to one of the plurality of memory cells may be performed by enabling a specific word line through a row address and by enabling a specific bit line through a column address. The access operation may include a write operation and a read operation, for example. The write operation may write data to a selected memory cell, and the read operation may read data from a selected memory cell. In a normal operation of a conventional semiconductor memory device, the word lines may be enabled one by one. However, in order to test semiconductor memory devices in mass production, a testing operation may require that the word lines and bit lines be enabled at the same time to reduce a testing time. A multi-word line test method for enabling a plurality of word lines at the same time during a testing operation may be referred to as an Address Don't Care scheme (“ADC scheme”). The ADC scheme may be a type of row address coding.
Generally, a number of memory cells coupled to a bit line may be 2n, where n is an integer greater or equal to two. For example, a number of memory cells may be 256Cell/BL per memory cell block, for example. However, if the number of memory cells coupled to a bit line is not 2n, inefficiency in the testing operating may exist when the ADC scheme is used. A 320Cell/BL or 416Cell/BL memory cell block may be an example of when the number of memory cells coupled to the bit line is not 2n. When a specific address becomes “Don't Care” to test the 320Cell/BL or 416Cell/BL memory cell block, word lines corresponding to the specific address may be selected at the same time. Some of the selected word lines may be not enabled due to an insufficient capacity of an internal boosted voltage power of the semiconductor memory device.
FIG. 8 illustrates a conventional row address coding method for the 256Cell/BL memory cell block. Referring to FIG. 8, the memory cell block may include 64 cell blocks. The 64 cell blocks may be divided into four parts, where each part includes 16 cell blocks. The four parts may be L0-L15, L16-L31, R0-15 and R16-R31. The 256Cell/BL memory cell block may include row addresses RA0˜RA13, and a total number of row addresses may be 16K, where K is 2n. In this particular example, n may be 10. The row addresses RA8˜RA13 may be referred to as higher-level row addresses, where each row address RA8˜RA13 may determine the coding for the 64 cell blocks. Three middle-level row addresses RA5˜RA7 may determine the coding for eight word line enable signals NWEIB1 within each cell block.
Furthermore, row addresses RA2˜RA4 may determine a coding of eight word line enable signals NWEIB0. Row address RA0 and RA1 may determine the coding for four word lines. That is, one of the word lines of 16K-number is selected by the 14-bit row address coding and activated.
FIG. 9 illustrates a conventional multi-word line test through the cell block coding of FIG. 8. Referring to FIG. 9, multi-word line 2 (MWL2) may indicate that two word lines may be enabled within one cell block in the multi-word line test when row address RA7 becomes “Don't care.” In other words, one word line per four word line enable signals NWEIB1 may be enabled. Multi-word line 4 (MWL4) may indicate that four word lines may be enabled within one cell block in the multi-word line test when row addresses RA7 and RA6 become “Don't care.” Multi-word line 8 (MWL8) may indicate that eight word lines may be enabled within one cell block in the multi-word line test when row addresses RA7, RA6 and RA5 become “Don't care.” Multi-word line 16 (MWL16) may indicate that 16 word lines may be enabled within one cell block in the multi-word line test when RA7, RA6, RA5 and RA4 become “Don't care.”
As shown in FIG. 9, as the number of row addresses become “Don't care” increases by one, an enabled interval of word lines may be reduced by half, and the number of enabled word lines may double. When using an address of RA8 or more, the enabled word lines may exceed a range of the memory cell block. In addition, when using an address of RA3 or below, an interval between word lines may become too narrow. As a result, the conventional address coding scheme for a 256Cell/BL memory cell block may be difficult to apply. In addition, in the 256Cell/BL memory cell block, row addresses capable of becoming “Don't Care” may be limited to four row addresses RA4˜RA7, and the application of the multi-word line test may be only valid from the multi-word line 2 (MWL2) to the multi-word line 16 (MWL16).
FIG. 10 illustrates a conventional row address coding method for the 320Cell/BL memory cell block. For the 320Cell/BL memory cell block, row addresses RA6˜RA13 may be used for the coding of 52 cell blocks. The only addresses capable of becoming “Don't Care” in the multi-word line test for the 320Cell/BL memory cell block may be RA4 and RA5.
FIG. 11 illustrates a conventional multi-word line test through the cell block coding of FIG. 10. For performing the multi-word line test through the cell block coding of FIG. 10, only multi-word line 2 (MWL2) and multi-word line 4 (MWL4) may be applied. As a result, because only a total of four word lines may be enabled, a test time may increase as compared with the 256Cell/BL coding described above.